Along with a trend toward high integration of semiconductor devices, a wiring or an isolation width required for a manufacturing process is being miniaturized. Further, as three-dimensionallization of semiconductor devices advances, it is required to form, e.g., a long and deep line or hole shape having a high aspect ratio. In addition, various materials are used for semiconductor devices, so that it is required to deal with etching of various materials.
Therefore, in a semiconductor device manufacturing process, a sufficient etching selectivity may not be obtained by a current photoresist. In that case, a photoresist pattern is transferred to another film referred to as a hard mask film and, then, a processing target film below the hard mask film is etched while using the hard mask film as a mask (see, e.g., Patent Document 1).
The hard mask film serves as an etching mask and is not necessary in a semiconductor device. Therefore, the hard mask film on the processing target film in the semiconductor device is removed during the manufacturing process. Currently, in removing the hard mask film on the processing target film, wet etching (wet cleaning) is used as disclosed in, e.g., a paragraph [0024] of Patent Document 1. In the wet cleaning, liquid remains in a processing pattern and, thus, dry processing is required after the wet cleaning. However, if the miniaturization of semiconductor devices further progresses, a processing pattern becomes thinner and deeper. Therefore, the processing target film formed in the processing pattern is easily affected by surface tension of the liquid remaining in the pattern and may be destroyed during the dry processing.
As for a technique for preventing destruction of the pattern of the processing target film, gas chemical etching attracts attention (e.g., Patent Document 2). The gas chemical etching is a technique for chemically etching a film by using a reactant gas such as HF gas, NH3 gas or the like.
Patent Document 1: Japanese Patent Application Publication No. 2012-204652
Patent Document 2: Japanese Patent Application Publication No. 2007-134379
However, in the case of employing the gas chemical etching, a non-volatile component or a non-reactant component contained in a removal target (hard mask film) remains on a surface of the processing target film. A residue caused by the non-reactant component or the non-volatile component causes adverse effect on patterning. Therefore, the residue needs to be removed. However, when the residue and the processing target film have the same component, it is difficult to ensure a selectivity between the residue and the processing target film even by performing a residue removal process using a gas that reacts with the residue and, also, the processing target film may be adversely affected by the residue removal.
When fine particles exist in a space portion of a fine mask pattern, the particles become a mask and, thus, a shape defect may occur after the patterning of the processing target film.